The present invention relates to methods and apparatus for air curing tobacco and bringing it into condition.
Conventional air-curing tobacco barns utilize natural convection, with air flow generally proceeding from the bottom of the barn toward the top of the barn. In curing tobacco by the procedure generally referred to as the xe2x80x9cbulk curingxe2x80x9d method, tobacco leaves are loaded in a relatively compact mass on racks or in containers and placed inside of an enclosed curing barn where a furnace or a plurality of heaters circulate a forced flow of heated air through the mass of tobacco leaves to effect curing and drying. Conventional tobacco curing barns attempt to obtain the desired atmospheric conditions such as temperature and humidity within the tobacco barn by various adjustments of louvers or openings in the sides of the barn and the operation of heaters spaced along the floor of the barn with respect to the prevailing temperature and moisture content of the outside atmosphere, the wind velocity and its direction with respect to the tobacco barn. A number of problems have been observed when curing tobacco in conventional air-curing barns. The different tiers of tobacco stacked in the barn cure at different rates, the tips of the tobacco leaves are often found to dry too quickly, during dry ambient weather, the tobacco may dry too quickly and have poor quality, and during humid ambient weather the tobacco may rot and have poor quality along with elevated contents of tobacco specific nitrosamines.
In view of the above-noted problems with conventional methods and apparatus for curing tobacco, an embodiment of the present invention includes the aspects of an enclosure in which tobacco plants can be air cured, at least one vertically arranged air duct positioned in a central portion of the enclosure, the at least one vertically arranged air duct enclosing at least one in-line fan positioned in a vertical portion of the at least one vertically arranged air duct, at least one ventilating fan located in an upper portion of the enclosure, and at least one openable and closeable opening in at least one side wall of the enclosure. Temperature and humidity sensors can also be provided both inside and outside of the enclosure, with a programmable control system receiving input from the temperature and humidity sensors and providing controlling output to at least one of the in-line fan, the ventilating fan and/or the openable and closeable openings in the side of the enclosure.
According to another aspect of the invention, a method for air curing tobacco includes the tobacco being hung in an enclosure having at least one vertically arranged air duct positioned in a central portion of the enclosure, at least one in-line fan positioned in a vertical portion of the at least one vertically arranged air duct, at least one ventilating fan located in an upper portion of the enclosure and at least one openable and closeable opening in at least one side wall of the enclosure, with the method including the steps of opening the at least one opening, and operating the at least one ventilating fan to force air down through the tobacco from the upper portion of the enclosure. In another aspect of the invention the method of curing tobacco can include the steps of closing the at least one opening and introducing an aqueous solution or steam into a lower portion of the at least one vertically arranged air duct and operating the at least one in-line fan to diffuse the moisture and drive it upwards through the vertically arranged air duct.